1. Field of the Invention
Aspects of the present invention relate to a holographic information recording and/or reproducing apparatus, and more particularly, to a holographic information recording and/or reproducing apparatus using a single side incidence method for enhancing efficiency of an optical system.
2. Description of the Related Art
Recently, technologies for recording information using a hologram have become available on the market. According to an information recording method using the hologram, information is stored in a light sensitive inorganic crystal or polymer material in an optical interference pattern. Optical interference fringes are formed by using two laser beams having coherency. That is, information is recorded by optical interference fringes, which are formed by interference between a reference light and a signal light having difference paths, causing a chemical or physical change on a photosensitive storage medium. In order to reproduce information from such a recorded interference pattern, a reproduction light similar to the reference light used when recording is illuminated onto the interference pattern recorded on the storage medium. This reproduction light causes diffraction due to the interference pattern, whereby the signal light is restored and the information is reproduced.
In the hologram information recording technology, there is a volume holography method in which recording and reproducing are performed in a page unit using volume holography, and there is a micro holography method in which recording and reproducing are performed in a single bit unit using micro holography. The volume holography method has an advantage in that bulk information can be processed at the same time. However, since an optical system is minutely controlled, it is difficult for the volume holography method to be commercialized for an information storage apparatus for general users.
The micro holography method records information in a storage medium in a three dimensional method by forming a minute interference pattern by making two concentrated beams interfere with each other at a focus and forming an information plane by moving the interference fringes on a plane of the storage medium. The micro holography method layeredly records the information plane in a depth direction of the storage medium. However, a conventional recording and/or reproducing apparatus using the micro holography method includes an optical system for a signal light and an optical system for a reference light, each light being illuminated onto both sides of a storage medium. Thus, the illuminating of the signal light and the reference light onto both sides of the storage medium results in complexity for an optical system.